Integrated Soft Ionotronic Skin with Stretchable and Transparent Hydrogel-Elastomer Ionic Sensors for Hand-Motion Monitoring.

Skin-like stretchable sensors with the flexible and soft inorganic/organic electronics have many promising potentials in wearable devices, soft robotics, prosthetics, and health monitoring equipment. Hydrogels with ionic conduction, akin to the biological skin, provide an alternative for soft and stretchable sensor design. However, fully integrated and wearable sensing skin with ionically conductive hydrogel for hand-motion monitoring has not been achieved. In this article, we report a wearable soft ionotronic skin (iSkin) system integrating multichannel stretchable and transparent hydrogel-elastomer hybrid ionic sensors and a wireless electronic control module. The ionic sensor is of resistive type and fabricated by curing ionic hydrogel precursor on a benzophenone-treated preshaped elastomer to form a hydrogel-elastomer hybrid structure. The hydrogel-elastomer hybrid iSkin is highly stretchable (∼300% strain), transparent (∼95% transmittance in the visible light range), and lightweight (<22 g). Experiments demonstrate that the fully integrated iSkin system can conformably attach onto the dexterous hands for recognizing the joint proprioception and hand gesture, and understanding the sign language. Our iSkin system would also provide a test bed for customized material selection and construction in a variety of applications.

Li dopant induces moisture sensitive phase degradation of an all-inorganic CsPbI2Br perovskite.

All-inorganic halide perovskites without volatile components have great potential for long term thermal stability. However, the phase stability of all-inorganic perovskites is sensitive to moisture and has been seldom studied. In this work, the phase stability of α-CsPbI2Br was studied in different relative humidity conditions. The moisture resistance of α-CsPbI2Br can be significantly enhanced by using a polymer or organic molecule capping layer including Spiro-MeOTAD. Although an all-inorganic CsPbI2Br perovskite based device using the typical Li salt doped Spiro-MeOTAD layer could offer an efficiency up to 12.6%, it exhibited even worse moisture resistance than a bare perovskite film under the same ambient conditions. This unusual phenomenon is ascribed to the hygroscopic properties of Li-TFSI inducing moisture sensitive phase degradation. Therefore, it is desirable to decrease the amount of, or avoid the Li salt, as a dopant for stable all-inorganic perovskite solar cells with balanced stability and high performance.

The best body spot to detect the vital capacity from the respiratory movement data obtained by the wearable strain sensor.

[Purpose] The purpose of this study is to find the best body spots on the chest and abdomen wall to obtain the correlated indicators to the vital capacity. [Subjects and Methods] Thirty healthy male staff of the center served as the participants were advised to conduct a breathing movement using spirometer and a wearable strain sensor (WSS) respectively, which was the measured at four spots on chest and abdomen wall from maximal end of inspiration to maximal end of expiration. The Pearson's correlation analysis was conducted to find the correlation of the data obtained respectively by the WSS and spirometer. [Results] The correlation of the mobility data at the four body spots to the vital capacity data were calculated for each level by means of Pearson's correlation coefficient, which showed that the values at each body spot were positive significant correlations and the highest value was at the 10th rib. [Conclusion] There was a correlation between the mobility data of the chest and abdomen obtained by the WSS and the vital capacity data obtained by the spirometer, for which, the 10th rib is the best body spot to detect the positive significant correlation.

Large Area One-Step Facile Processing of Microstructured Elastomeric Dielectric Film for High Sensitivity and Durable Sensing over Wide Pressure Range.

Once the requirement of sensitivity has been met, to enable a flexible pressure sensor technology to be widely adopted as an economic and convenient way for sensing diverse human body motions, critical factors need to be considered including low manufacturing cost, a large pressure detection range, and low power consumption. In this work, a facile approach is developed for one-step processing of a large area microstructured elastomer film with high density microfeatures of air voids, which can be seamlessly integrated into the process flow for fabricating flexible capacitive sensors. The fabricated sensors exhibit fast response and high sensitivity in the low pressure range to be able to detect very weak pressure down to 1 Pa and perform reliable wrist pulse monitoring. Compared to previous work, more advantageous features of this sensor are relatively high sensitivity being maintained in a wide pressure range up to 250 kPa and excellent durability under heavy load larger than 1 MPa, attributed to the formed dense air voids inside the film. A smart insole made with the sensor can accurately monitor the real-time walking or running behaviors and even a small weight change less than 1 kg under a heavy load of a 70 kg adult. For both application examples of wrist pulse monitoring and smart insole, the sensors are operated in a 3.3 V electronic system powered by a Li-ion battery, showing the potential for power-constrained wearable applications.

High efficiency air stable organic photovoltaics with an aqueous inorganic contact.

We report a ZnO interfacial layer based on an environmentally friendly aqueous precursor for organic photovoltaics. Inverted PCDTBT devices based on this precursor show power conversion efficiencies of 6.8-7%. Unencapsulated devices stored in air display prolonged lifetimes extending over 200 hours with less than 20% drop in efficiency compared to devices based on the standard architecture.

[Fluorescence spectra of rubrene dopant for organic light-emitting devices].

The effect of concentration of 5, 6, 11, 12-tetraphenylnaphthacene (rubrene) yellow dye in solution on fluorescence performance was studied through various concentrations. Also the photoluminescence (PL) spectra of rubrene solution with various concentrations were measured to investigate the concentration effect, which is beneficial to obtaining an optimum concentration at maximum PL intensity without concentration quenching. One hand was to focus on the range of concentration for quenching. The other hand was to change the solution concentration in the range of concentration. The results showed that the PL intensity was the highest at a rubrene concentration of 2 x 10(-3) mol x L(-1), which was fixed on a concentration range from 10(-3) to 10(-2) mol x L(-1). And it was decreased only 11% with the increase in concentration after the optimum concentration. The PL spectra of rubrene: N,N'-Bis(naphthalen-1-y)-N,N'-bis(phenyl)benzidine (NPB) blending system with various proportions in solution were also measured, indicating that the inefficient energy transfer between NPB and rubrene leads to white fluorescence light emission. It was better to realize blue and yellow fluorescence from NPB and rubrene, so the white light was obtained.